The Wnt genes encode a large and highly conserved family of secreted growth factors. During normal development, transcription of Wnt family genes is tightly regulated both temporally and spatially. To date, 19 Wnt proteins have been discovered in humans. All of the Wnt proteins are 38- to 43-kDa cysteine-rich glycoproteins. Wnts have a range of roles during development, governing cell fate, migration, proliferation and death. These include body axis formation in zebrafish and xenopus, wing and eye development in drosophila and brain development in mice (Parr, et al. (1994) Curr. Opinion Genetics & Devel. 4:523-528, McMahon A P, Bradley A (1990) Cell 62: 1073-1085). In adults the role of Wnts is thought to be linked to maintaining tissue homeostasis with aberrant signalling implicated in a variety of cancers.
Wnt-mediated signalling occurs through binding of Wnt ligand to frizzled (Fzd) proteins, seven-transmembrane receptors. These receptors contain an N-terminal cysteine rich domain (CRD) which serves as the Wnt binding domain. Binding is stabilised by low-density-lipoprotein receptor-related proteins 5 and 6 (Lrp5 and Lrp6) (He, et al. (2004) Dev Apr; 131(8):1663-77). Fizzled ligation by Wnt is known to activate at least three different signalling pathways including the “canonical” β-catenin pathway, “non-canonical” planar cell polarity (PCP) and calcium pathways. Wnt signalling is further regulated by alternative receptors, including Ror2, secreted antagonists, such as WIF-1 (Hsieh, et al. (1999) Nature Apr. 1; 398(6726):431-6) and alternative Wnt receptors, such as Dickkopf (DKK) (Niehrs C (2006) Oncogene December 4; 25(57):7469-81).
When inactive, β-Catenin is rapidly turned over by a conglomeration of several proteins known as the “destruction complex”. The complex consists of Axin, adenomatous polyposis coli (APC), casein kinase (CK)-1a and glycogen synthasekinase (GSK)-3β (Hamada, et al. (1999) Science 12; 283(5408):1739-42). In this state, β-catenin is phosphorylated on serine-threonine on the amino terminus leading to ubiquitination (Behrens, et al. (1998) Science 280: 596-599). In the canonical pathway of Wnt activation, Wnt-ligated Fzd binds to and activates cytoplasmic Dishevelled (Dvi) (Chen, et al. (2003) Science 301:1391-94). Wnt-ligated Lrp5 and Lrp6 directly bind to cytoplasmic Axin, inhibiting its function as a destruction complex stabiliser (Zeng, et al. (2008) Dev. 135, 367-375). These associations lead to a destabilisation of the destruction complex and cytosolic accumulation of β-catenin. Stabilisation and accumulation of β-catenin leads to nuclear translocation where it complexes with T cell factor/lymphoid enhancer factor (TCF/LEF) high mobility group transcription factors and promotes transcription of target genes such as Cyclin D1, p21 and cMyc.
Oncogenic mutations in the β-catenin gene CTNNb1 exclusively affect specific serine and threonine and surrounding residues vital for targeted degradation by APC (Hart, et al. (1999) Curr. Biol. 9:207-210). This interaction is especially apparent in colorectal cancer, where the majority of tumours present with APC mutations and an increased proportion of the remainder express CTNNb1 mutations (Iwao, et al. (1998) Cancer Res Mar. 1, 1998 58; 1021).
Many recent studies have investigated compounds targeting β-catenin or other downstream Wnt pathway proteins. Recent research suggests that modulating Wnt-Wnt receptor interaction at the cell surface is effective in reducing cell oncogenicity. This has been shown in systems with tumourgenicity driven by Wnt ligand overexpression (Liu, et al. (2013) PNAS 10; 110(50):20224-9) and where Wnt expression is driven by downstream pathway activation (Vincan et al., Differentiation 2005; 73: 142-153). Vincan et al transfected non-functional Frd7 receptor into a SK-CO-1 cell line with a homozygous APC mutation driving Wnt pathway activation. These cells demonstrated modulated morphology and reduced tumour-forming efficiency compared to parental cells in a xenograft model. This data suggests that modulating Wnt ligand-mediated signalling may have a beneficial effect even in malignancies with downstream Wnt pathway mutations.
The described invention is proposed to inhibit Wnt-mediated signalling. This includes paracrine signalling in the tissues surrounding tumours and autocrine and paracrine signalling in cancer cells.
Wnt proteins undergo post-translational modification, shown in several mutation experiments to be vital for effective protein trafficking and secretion (Tang, et al. (2012) Dev. Biol 364, 32-41, Takada, R. et al (2006) Dev. Cell 11, 791-801). Palmitoylation of Wnt proteins occurs at several conserved amino acids (C77, S209) and is performed by porcupine, an O-acetyltransferase, in the endoplasmic reticulum. Mutations in porcupine have been shown to be the cause of developmental disorders, including focal dermal hypoplasia, through impaired Wnt pathway signalling (Grzeschik, et al. (2007) Nat. Genet, 39 pp. 833-835). The dependence of Wnt ligand signalling on porcupine and the body of evidence linking Wnt pathway signalling to cancer has led to porcupine being identified as a potential anti-cancer target.
US 2014/0038922 discloses compounds that inhibit the Wnt signalling pathway and the use of these compounds in the treatment of Wnt signalling-related diseases. Similarly, WO 2012/003189 and WO 2010/101849 disclose compounds and methods for modulating Wnt signalling pathway.
An aim of the present invention is to provide alternative or improved Wnt signalling modulators. For example, an aim of the present invention is to provide alternative or improved Wnt signalling inhibitors, optionally inhibitors of porcupine.
Furthermore, it is an aim of certain embodiments of this invention to provide new compounds for use in: Wnt mediated diseases, such as secreted Wnt ligand mediated diseases which may be treated by inhibition of porcupine; treating cancer, sarcoma, melanoma, skin cancer, haematological tumors, lymphoma, carcinoma, and leukemia; or enhancing the effectiveness of an anti-cancer treatment.
It is an aim of certain embodiments of this invention to provide new cancer treatments. In particular, it is an aim of certain embodiments of this invention to provide compounds which have comparable activity to existing treatments, ideally they should have better activity. Certain embodiments of the invention also aim to provide improved solubility compared to prior art compounds and existing therapies. It is particularly attractive for certain compounds of the invention to provide better activity and better solubility over known compounds.
It is an aim of certain embodiments of this invention to provide compounds which exhibit reduced cytotoxicity relative to prior art compounds and existing therapies.
Another aim of certain embodiments of this invention is to provide compounds having a convenient pharmacokinetic profile and a suitable duration of action following dosing. A further aim of certain embodiments of this invention is to provide compounds in which the metabolised fragment or fragments of the drug after absorption are GRAS (Generally Regarded As Safe).
Certain embodiments of the present invention satisfy some or all of the above aims.